1. Field of the Invention
The invention relates to a navigation system for guiding a driver in a vehicle, the system comprising
read means for reading chain information from a storage medium comprising a first storage unit with chains and nodes, a chain representing a road element and being connected to another chain via a node, PA1 process means for exploiting said chain information, for example a planning module for planning a route or a display module for displaying a map on a display, and PA1 a receiver for the reception of a traffic message related to a pre-defined problem location.
The invention further relates to a storage medium for use in a navigation system, the storage medium comprising a first storage unit with chains and nodes, a chain representing a road element and being connected to another chain via a node.
2. Description of Related Art
Such a system is described in the article "Traffic messaging, dynamic updating and road database standards the major issues", S. Queree and T. Wood, IEE Colloquium on `Prometheus and Drive` (Digest No. 172), pp. 9/1-3, Oct. 15, 1992. This computer assisted driver information system comprises a digital map representing the roads and junctions on which the driver can travel. The digital map resides on some storage medium that can be read by the navigation system. Based on the information in the map, the navigation system guides the driver during his journey. The digital map on the storage medium is static in that it reflects the information of roads at the moment the data for the storage medium is manufactured. Later changes to the roads after the storage medium has been manufactured are not present. The known system includes a receiver for the reception of traffic messages that are broadcast according to the Radio Data System (RDS). In RDS, the message is broadcast together with the audio signals of a radio program and the RDS receiver in the vehicle can receive the combined signals and separate the message from the audio. Within RDS, the Traffic Message Channel (TMC) is a set of coded traffic messages, agreed by the European Conference of Ministers of Transport (ECMT) and laid down in the pre-standard prENV/278/4/1/0010. The traffic message according to TMC provides, among others, an event and a location. An event relates to a happening or circumstance of importance to a driver, like a temporary road closure, slow traffic on a road or fog. A large number of events have been standardised and the message contains a code indicating such standardised event. The location in the traffic message indicates the area, highway segment or point location where the source of the problem is situated. In a country, the respective authority has defined a number of potential problem locations in advance and has given these locations a unique number. The traffic message contains such problem location number to identify the problem location at hand.
After the receiver has received the traffic message, the system consults on the basis of the code and problem location number a local table to establish the event and the problem location of the traffic message. Subsequently the driver is informed through a spoken message and/or a written message. The traffic messages are typically intended directly for the driver and have been coded in isolation from the digital map of the navigation system. Therefore, the messages cannot be processed by the navigation system and cannot be used to update the static digital map on the storage medium, but are only supplied to the driver.